A number of suspected impact craters have been linked to the so-called Great Dying at the end of the Permian 250 million years ago. This was a time when 90% of marine life and 80% of life on land were wiped out.

But, says von Frese, his is the best candidate for the killer crater.

First, he says, the circular land features analysed in the Wilkes Land region of East Antarctica, south of Australia, suggest a big enough impact to have caused catastrophic damage to Earth.

At 480 kilometres wide, the crater would be more than twice the size of the Chicxulub crater, formed from the impact believed to have wiped out the dinosaurs much later, say the researchers.

Second, says von Frese, evidence, including its location, suggests it is older than 100 million years, the date at which Australia drifted northwards from Gondwana.

Third, the landform has a special telltale feature of impact craters at its centre, a 320 kilometre wide plug of dense material, says von Frese. This is expected to be mantle material that was sucked up as the meteorite rebounded from the Earth's surface.

This so-called mascon is a well known feature of craters on the Moon, says von Frese, who studies lunar impact craters.

And he says no other suspected craters linked to the Permian extinction show this feature.

Gravity measurements

Von Frese and team mapped the crater using two different sets of measurements.

Gravity measurements taken by NASA's Grace Satellites show a higher readings in the centre of the crater.

This corresponds to the slightly raised area of the mascon, detected by another imaging method, says von Frese.

But what was interesting was that the coastline, where Australia would have fitted together with Antarctica, took a 'bite' out of the concentric rings or shock waves, around the crater.

Von Frese says this suggests that the ocean between Antarctica and Australia opened after the crater was formed.

He thinks the meteorite that caused the crater could have hit 250 million years ago, triggering a process that culminated in the break up of Gondwana 100 or so million years later.

Mixed reception

Von Frese's report has been met with a mixed response from the Australian scientific community.

"I'm quite excited about the possibility that this is another crater," says Dr Peter Morgan, of the University of Canberra.

Morgan trained in gravity analysis at Ohio State University and says he has ground-based gravity and radar measurements of the same area.

He says he will now make it a priority to process the data and share it with the other researchers to see if it supports the theory.

Earth scientist, Professor John Talent, of Sydney's Macquarie University says before the land structure can be linked to the Permian extinction, a precise age for it is needed.

Von Frese's team did not directly date the crater; it's almost 2.5 kilometres beneath the ice.

Talent also says that research in the past couple of years suggests the Permian extinction was a result of a number of events extending over several million years rather than an instantaneous impact.

Vulcanologist Peter Whitehead, of James Cook University in Cairns says volcanic activity played a central role in the Permian extinction.

He says one suggestion has been that meteorite impacts send shock waves through the Earth and cause volcanic activity on the other side of the planet.